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Art
Joined: 09 Nov 2005
Posts: 647
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 Posted: Wed Aug 16, 2006 2:25 pm Post subject: Parity Check (odd/even) |
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Hi,
I've run into trouble with an encryption routine I'm trying to clone.
What is the quickest and easiest syntax in C for checking if a byte value
is odd or even?
I tried searching on Google, but mention "Parity" and it's all about error checking.
Thanx, Art. |
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groepaz
Joined: 01 Sep 2005
Posts: 305
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Art
Joined: 09 Nov 2005
Posts: 647
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| Posted: Wed Aug 16, 2006 3:35 pm Post subject: |
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Thanx groepaz :)
Is that checking the LSB?
why is bit0 called bit 1?
I guess it all depends on what the "&" is if it's an and I might learn something here.. |
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groepaz
Joined: 01 Sep 2005
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Samstag
Joined: 24 Nov 2005
Posts: 5
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| Posted: Wed Aug 16, 2006 9:15 pm Post subject: |
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| groepaz wrote: | | if(value&1){ /* odd */ }else{ /* even */} |
That's not a parity check, though. You'd want something more like:
| Code: | byte parity = 0;
for(i = 0; i < 8; i++)
{
if(value & 1)
parity = !parity; // toggle parity status
value = value >> 1; // rotate bits right
} |
Untested. |
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groepaz
Joined: 01 Sep 2005
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Samstag
Joined: 24 Nov 2005
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| Posted: Wed Aug 16, 2006 9:32 pm Post subject: |
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| Ah, well that's certainly true :) |
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Art
Joined: 09 Nov 2005
Posts: 647
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| Posted: Thu Aug 17, 2006 6:55 am Post subject: |
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That's what I meant.
One of the web definitions for parity:
"The quality of being either odd or even" |
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siberianstar
Joined: 22 Jun 2006
Posts: 70
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| Posted: Thu Aug 17, 2006 7:52 am Post subject: |
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| "Parity check" in informatic language is used to define the algorithm to check data errors on trasmission between pc and serial ports. |
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